Since I will be replacing my cat with a free flow cat soon, I might as well keep the air flowing and replace the exhaust from the cat back. Everyone and their sister has dual exhaust coming out under the rear bumper. Is there any performance gain from the dual exhaust? I am inclinded to just have it dump out the side where the stock location is....or I might just get a muffler and dump pipe it. Just trying to understand the trend to double exhaust out the back.

 

the true restriction on our rigs is the factory Y pipe.. if you really want to do some good, start just north of the cat, and get rid of that Y- replace it with an offroad from Jegs, MagnaFlow, or have the shop fab one up for you.. if you keep that thing, anything you do south of it will be a waste of time and money..

on a similar note: I have shorty headers that I put on previous to going true dual.. I bet a dollar to a donut that the OE manifolds breathe just as good as the shorties I have.. I couldn't understand why the headers did zilch for me, until I pulled that OE Y.. then I understood clearly..

One of my greatest regrets during my trucks transformation is not taking pictures of that Y after I cut it open.. it basically crammed two 2.25" pipes into one 2.5" pipe, and the body of the Y was just a sleeve squeezing them together.. CHOKE CENTRAL..

You'll be FAR better served cutting it out.. The muffler makes a difference (whether you do one in one out, or one in two out) but it's not near the difference removing that dang Y will make.

 

http://www.ehow.com/about_5575904_du...e-exhaust.html

Everything you need to know.

 

Drew. I plan on doing the magnaflow direct fit cat. I am assuming they upgraded the Y pinch point issue. Correct me if I am wrong.

Then out the back from the direct fit cat, cut just in front of the stock muffler and take out all old pipe and tie in the new muffler and pips. Or...possibly just add a flowmaster 50 muffler into the line with some extra straight pipe and clamps into the stock pipe system.

 

Yeh, I realize that true dual has great advantages...but I am not going the true dual exhaust. And I am guessing that 99% of the trucks on the road today with dual pipes out the back are only splitting after the muffler. I have yet to see where that has any performance advantage. Just looks. Please correct me if I am wrong.

 

They have 2 mufflers, they Y after the cat.

 

most often they are running one in/two out mufflers.. the gain here, if any, is slight and simply due to the fact you have basically doubled your pipe size AFTER the muffler.. after being operative word.. meaning, you haven't done too much at all... split pipe mufflers are more for sound and looks..

the direct fit Magna will use the OE Y that's on your rig now.. it will be cut directly in front of the cat and the new one welded in.. that's why it's called 'cat-back'.. it does NOT address the Y or the crossover.. The OE Y is the biggest thing to rid yourself of if you're looking for gains out of re-working your exhaust..

true duals are the best option, but w/ this caveat: they need to be connected somewhere to 'drag pulses'.. an H or an X pipe will do this.. so will a really well designed Y (which is NOT true dual)...

you're engine is only strong enough to push the pulses out of the way so far down your exhaust system.. it needs help to clear one pulse for the next pulse on it's little conveyor system.. hot spots, such as a catalytic converter help this (but the cat negates any help because it clogs up by it's very nature).. also effective are vacuum effects created by passing/crossing pulses which keep the tubes nice and hot as well as create an area of low pressure right behind them- which pulls on the following pulse about the same time it starts to slow down from the engines push..

anyway, exhaust theory is an exhausting subject.. bottom line: for your purposes, lose the OE Y.. split the exhaust by using a one in/two out muffler if you want, it doesn't matter as far as performance is concerned.. it does for sound.. and looks.. it will be so close to the same as 'splitting pipes' as it is to not.. your call..

if you don't cut out the Y, you're not really improving but very little (by introducing a high flow cat and better flowing muffler).. the OE Y- THAT, is the issue dude.

 

The way I see it in this picture of the magnaflow direct fit hi-flow cat converter, it looks like the Y is being replaced. Maybe I am not clear on where the Y is you are referring to.

 

I stand corrected..

 

Phew! I thought there was another "Y" I had to be concerned about.

So, after the cat and then flowmaster, it doesn't matter if it went 3" single pipe, or split 2.5" pipe. The flow restriction is already done just before the cat.

So my theory is that there is no increase in performance or sound from a system that splits to dual exhaust below the rear bumper from that of a single exhaust dumping out the side (in front of tire, or behind the tire, or a dump pipe).